The River Sem is a natural waterway that flows through the ceremonial county of
Wiltshire
Wiltshire (; abbreviated Wilts) is a historic and ceremonial county in South West England with an area of . It is landlocked and borders the counties of Dorset to the southwest, Somerset to the west, Hampshire to the southeast, Gloucestershir ...
in England. It flows approximately from its source near
East Knoyle to join the
River Nadder
The River Nadder is a tributary of the River Avon, flowing in south Wiltshire, England.
Course
The river flows north from Ludwell to West End where it is joined by the Ferne Brook, close to the Lower Coombe and Ferne Brook Meadows site of specia ...
near
Wardour.
Course
The source is Summerleaze Pond near East Knoyle, just east of the
A350. The river flows southeast to Pondhead Copse, below which it flows through two large ponds: Brach Pond and Eeelstage Pond. It then turns east and flows under Savage Bridge and Share Lane before reaching the Nadder, northwest of Wardour.
Tributaries
The river is fed by several small waterways. On its south bank, a stream with a source near Whitebridge Farm southeast of
Sedgehill
Sedgehill is a former civil parish, with scattered small settlements, now within Sedgehill and Semley civil parish in the southwest of the English county of Wiltshire. It lies to the west of the A350 primary route, about north of Shaftesbury, ...
, again close to the A350, flows east to join the Sem near Billhay Farm, above Pondhead Copse.
Also on the south bank, it is fed by a stream that has its source in Bennet's Copse near Hart Hill Stud Farm; this stream flows northeast through
Sem Hill
Semley is a village in Sedgehill and Semley civil parish in Wiltshire, England, about north-east of Shaftesbury in neighbouring Dorset. The hamlet of Sem Hill lies about a quarter of a mile west of the village.
The River Sem, from which the v ...
and Billhay Pond before joining the Sem at Pondhead Copse.
Geology
The underlying geology is that of
Kimmeridge Clay
The Kimmeridge Clay is a sedimentary deposit of fossiliferous marine clay which is of Late Jurassic to lowermost Cretaceous age and occurs in southern and eastern England and in the North Sea. This rock formation is the major source rock for Nor ...
overlaying
Limestone
Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms wh ...
. Faults between the two layers give rise to the springs that provide the source of the water for the river catchment.
Water quality
The Environment Agency measures the water quality of the river systems in England. Each is given an overall ecological status, which may be one of five levels: high, good, moderate, poor and bad. There are several components that are used to determine this, including biological status, which looks at the quantity and varieties of
invertebrate
Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...
s,
angiosperm
Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. They include all forbs (flowering plants without a woody stem), grasses and grass-like plants, a vast majority of br ...
s and fish. Chemical status, which compares the concentrations of various chemicals against known safe concentrations, is rated good or fail.
[ Text was copied from this source, which is available under a]
Open Government Licence v3.0
© Crown copyright.
Water quality of the River Sem in 2019:
References
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Sem